JP3535764B2 - Absolute encoder - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an improvement in an absolute encoder.

[0002]

2. Description of the Related Art An absolute encoder used as a sensor for detecting an angle forms marks for angle recognition on a rotating disc at predetermined angular intervals, and reads the marks for angle recognition to read the rotation circle. It is configured to detect the rotation angle of the plate.

[0003]

When the angle of the mechanical element is set to a predetermined angle based on the angle information output from the absolute encoder, the set angle includes a relatively large error. Become. Because in the absolute encoder, the angle recognition mark is formed wide along the circumferential direction of the rotating disc,
This is because there is an error range corresponding to the circumferential width.
Of course, if the arrangement angle intervals of the angle recognition marks are made smaller, the error range becomes smaller, but this causes an increase in the processing cost of the marks and an increase in the cost due to the increase in the number of arrangement bits of the reading element. . In view of such a situation, an object of the present invention is to provide an absolute encoder capable of accurately setting the angle of a mechanical element without making the arrangement angle intervals of the angle recognition marks close.

[0004]

According to a first aspect of the present invention, angle recognition marks are formed on a rotating disc at predetermined angular intervals, and the rotation angle of the disc is detected by reading the angle recognition marks. In the absolute encoder, on the circumference of the rotary disc, while forming the positioning marks with the circumferential width of the disc smaller than that of the angle recognition mark at the predetermined angular intervals, Three mark reading means for reading the positioning marks are arranged along the circumference, and the arrangement intervals of the mark reading means are set as follows.
The length is set to an integer multiple of the arrangement interval of the positioning marks plus a length corresponding to a predetermined allowable angle detection error range. In a second aspect based on the first aspect, the length corresponding to the allowable angle detection error range is set to the circumferential width of the positioning mark.

[0005]

1 is a plan view showing an embodiment of an absolute encoder according to the present invention. This absolute encoder AE is provided with an angle recognition mark M
1 to M3 and a light-shielding rotary disk 10 on which positioning marks M4 are formed, and a reading block 20 provided to read the marks M1 to M3 and M4.

Angle recognition marks M1, M2 and M3
Are equiangular division lines L0 to L0 on the disk 10,
L6 is provided at the intersection of the concentric arc lines C1 to C3, and the positioning mark M4 is an equal angle division line L.
It is provided at the intersection of the arc lines C4 and A, L0 to L6, LB. These marks M1 to M3 correspond to the disk 10
And a longitudinal axis of the circular plate 10 extending in the circumferential direction of the circular plate 10. Further, the mark M4 is the disc 1
It is composed of pores penetrating 0, and its diameter is marks M1 to M3.
Is much smaller than the length in the longitudinal direction. The mark M
1, M2 and M3 have weights of 20, 21, and 22, respectively. Further, in this embodiment, the equal angle division lines LA, L0 to L6 and LB are formed.
The division angle θ is set to 10 °.

As shown in FIG. 2 which is a sectional view taken along the line AA of FIG. 1, the reading block 20 includes the light projecting elements 21, 22, 23 and 24C arranged in the radial direction of the disk 10 and the disk 10. Light receiving elements 21 ', 22', 23 'which are arranged so as to face the light projecting elements 21, 22, 23 and 24C, respectively.
And 24C '. In addition, the light projecting element 21,
For example, light emitting diodes are applied to 22, 23 and 24C, and phototransistors are applied to the light receiving elements 21 ', 22', 23 'and 24C'.

The light projecting elements 21, 22 and 23 are located on the arc lines C1, C2 and C3 shown in FIG. 1, respectively. Therefore, the marks M1, M2, and M3 are formed between the elements 21 and 21 'as the disc 10 rotates.
It moves between the elements 22 and 22 'and between the elements 23 and 23', respectively. Then, for example, the elements 21, 2
In the state where the mark M1 is interposed between 1 ', the light projected from the element 21 is incident on the element 21' via the mark M1, and as a result, the element 21 'is turned on.

On the other hand, as shown in FIG. 8 which is a sectional view taken along line BB of FIG. 1, the light projecting element 24C is provided in the reading block 20.
The light projecting elements 24L and 24R located on the left and right sides of the disk 10
It is provided with light receiving elements 24L 'and 24R' facing the light projecting elements 24L and 24R with the light emitting element 24L and 24R interposed therebetween. Projection element 24
L, 24C, and 24R are respectively located on the arc line C4 shown in FIG. 1, and the arrangement interval thereof is a minute distance Δα (in this example, the arrangement interval α of the positioning marks M4, as shown in FIG. 8). , The distance of the diameter of the mark M4) is added.

The mark M4 on the arc line C4 is the disc 1
With the rotation of 0, the element 24L, 24L ',
It moves between C and 24C 'and between elements 24R and 24R'. Then, for example, as shown in FIG. 8, when the mark M4 is interposed between the elements 24C and 24C ', the light projected from the element 24C is incident on the element 24C' through the mark M4, and as a result, , The element 24
C'turns on.

FIG. 3 shows an array antenna 30 installed in a base station for mobile communication. The radiating elements 30a to 30f of the antenna 30 are connected to the wireless device 33 via variable phase shifters 31a to 31f and a distributor / combiner 32 which are separately provided for the radiating elements 30a to 30f. When changing the tilt angle of the radiation beam of the antenna 30, the phase of each output of the distributor / combiner 32 is changed by the variable phase shifters 31a to 31f. That is, for example, the variable phase shifters 31a,
If the phases of the respective outputs of the distributor / combiner 32 are changed by 10 °, 20 °, ... 60 ° by 31b, ... 31f, the tilt angle of the radiation beam is changed as shown in the figure.

The variable phase shifters 31a to 31f are provided with a common drive shaft 34 for interlocking them.
By changing the rotation angle of No. 4 by the drive device 35, the respective phase change amounts are set at the same time. Since the configurations of the variable phase shifters 31a to 31f are conventionally known, the description thereof will be omitted here. The drive shaft 34
In order to control the rotation angle of, the angle sensor for detecting the rotation angle is required. Absolute encoder A above
E can be applied as this angle sensor, and in this case, the drive shaft 34 becomes the drive shaft 10a of the disc 10.

The controller 36 controls the drive unit 35 based on the output of the absolute encoder AE, and executes the procedure shown in FIG. 4 to change the tilt angle of the radiation beam of the antenna 30. In this procedure, first, the elements 21, 21 ', 22, 2 shown in FIG.
Based on the reading results of the marks M1, M2 and M3 by 2'and 23,23 ', the current rotation angle of the drive shaft 34 is recognized (step 100). That is, FIG.
Although the drive shaft 34 is rotated by 30 °, both the light receiving elements 21 'and 22' are turned off and the light receiving element 23 'is turned on in this case. Therefore, the current rotation angle of 30 ° of the drive shaft 34 is recognized from the output states of these elements.

Next, the rotation direction of the drive shaft 34 is determined based on the target rotation angle and the current angle of the drive shaft 34 (step 101), and whether the determined rotation direction is the forward rotation direction. It is determined whether or not (step 102). Now, for example, if the target rotation angle is 60 °, the current angle is 30 °, and therefore, in step 101, the rotation direction of the drive shaft 34 is the forward rotation direction (counterclockwise direction in FIG. 1). It is determined. Then, in this case, the determination result of step 102 is YES.

Then, the actuator (for example, a DC motor) of the drive unit 35 is operated to rotate the drive shaft 34 in the forward rotation direction (step 103). Along with this, the mark M4 on the disk 10 shown in FIG. 8 moves to the right. As is clear from the arrangement of the marks M1 to M3 shown in FIG. 1, when the drive shaft 34 rotates to the target angle of 60 °, all the light receiving elements 21 ', 22' and 23 'are turned on. Therefore, it is determined whether or not the drive shaft 34 has rotated up to the target angle of 60 ° based on the output states of these light receiving elements (step 104). And the target angle 6
When the rotation to 0 ° is determined, the drive device 35 is decelerated and the drive shaft 34 is normally rotated at a lower speed than before (step 105).

At the time when all the light receiving elements 21 ', 22' and 23 'are turned on, the mark M1 shown in FIG.
One end of each of M2 and M3 is a light emitting element 21, 22 respectively.
This is the time when the optical axis positions of 23 and 23 are approached. At this time, as shown in FIG. 6, the optical axis of the light projecting element 24C is located on the right side of the mark M4 closest to this optical axis (the amount of deviation at this time is about half the width of the mark M1). Therefore, the light receiving element 24C 'is in the off state.

With the rotation of the drive shaft 34 at the low speed,
As shown in FIG. 7, the light receiving element 24L 'is turned on, and then,
As shown in FIG. 8, the light receiving element 24C 'is turned on. Therefore, in steps 106 and 107, the light receiving element 2
It is determined whether or not 4L 'and 24C' are turned on, and the actuator of the drive unit 35 is stopped when the ON operation of the light receiving element 24C 'is determined (step 108).

Next, it is judged whether or not the light receiving element 24R 'is turned on (step 109). When it is determined that the light receiving element 24R 'is not turned on, the drive shaft 34 is accurately positioned at the target rotation angle of 60 ° within the angular error range corresponding to the distance ± Δα / 2 (see FIG. 8). It was done.

On the other hand, if the drive shaft 34 overruns due to inertia or the like, the light receiving element 24R 'is turned on after the light receiving element 24C' is turned on.
The determination result of 09 is YES. Therefore, the drive device 35
Is operated to reversely rotate the drive shaft 34 at a low speed (step 110), and it is determined whether or not the light-receiving element 24C 'is turned on again (step 111). Stop (step 11)
2).

Next, it is judged whether or not the light receiving element 24L 'is turned on, that is, whether or not the drive shaft 34 is overrun in the opposite direction (step 113). If it is determined that the light receiving element 24L 'is not turned on, it means that the drive shaft 34 has been accurately positioned at the target rotation angle within the angular error range corresponding to the ± Δα / 2. finish. If the reverse overrun is determined, the procedure returns to step 105,
After that, the procedure of steps 105 to 113 is repeatedly executed until the determination result of step 109 or step 113 becomes NO.

According to the above procedure, the light receiving element 24 is finally obtained.
Since the rotation angle of the drive shaft 34 is controlled so that C'is turned on and both the light receiving elements 24L 'and 24R' are turned off, the rotation angle of the drive shaft 34 is controlled to the target rotation angle very accurately. It will be positioned. By positioning the drive shaft 34, the beam tilt angle of the antenna 30 is set to an angle corresponding to the positioning angle. When it is determined in step 102 that the drive shaft 34 is rotated in the reverse rotation direction, as shown in FIG.
The procedure of steps 103 'to 113' is executed. Since this procedure has contents similar to those of steps 103 to 113 shown in FIG. 4, the description thereof will be omitted here.

The distance Δα shown in FIG. 8 defines the positioning angle error of the absolute encoder AE, and the smaller the distance Δα, the smaller the angle error. For example, as shown in FIG. 9, if the distance Δα is set to ½ of the diameter of the mark M4 or slightly smaller than that, the error range becomes extremely small. In the example of FIG. 9, the light receiving elements 24L ', 24C' and 24
The angle of the drive shaft 34 will be finally adjusted so that all R'are turned on.

The distance Δα is appropriately set in consideration of the inertia of the drive shaft and the load connected to the drive shaft, the required height of positioning accuracy, and the like. That is, for example, when the inertia is large, the overrun phenomenon is repeated and the rotating shaft 34
Since it may take time to set the target angle to the target angle, the distance Δα is set to be large.

In the example shown in FIGS. 8 and 9, the element 24L (24L ') is different from the element 24C (24C').
And 24R (24R ') are arranged adjacent to each other,
As indicated by the chain line in these figures, the element 24C (24
Elements 24L (24L ') and 24R for C')
(24R ') may be arranged separately. Also, the element 2
4L (24L ') and 24R (24R') are the elements 2
4C (24C ') does not necessarily have to be arranged at a symmetrical position.

Since the absolute encoder AE is applied to the rotation angle control of the drive shaft 34 of the phase shifter 31 shown in FIG. 3, its detection angle range is limited to 0 to 60 °, but of course. It is also possible to adopt a configuration applicable to angle detection of 360 °. Further, in the above absolute encoder AE, the marks M1 to M3 and the mark M4 are formed by the through holes, but these marks may be formed by a light shielding material. In that case, the light receiving elements 21 'to 23', 24L ', 24C'
And 24R 'will be shielded by the mark.

[0026]

According to the present invention, on the circumference of the rotating disk,
Positioning marks are formed at a predetermined angular interval in which the width of the disc in the circumferential direction is set smaller than that of the angle recognition marks, and mark reading means for reading the positioning marks are provided along the circumference. Three pieces are arranged, and the arrangement interval of the second reading means is set to a size obtained by adding a length corresponding to a predetermined allowable angle detection error range to the length of an integral multiple of the arrangement interval of the positioning marks. There is. Therefore, if it is applied as an angle confirmation means when the angle of the mechanical element is set to a predetermined angle, the angle of the mechanical element can be accurately set based on the reading result of the positioning mark by the second reading means. Will be possible.

[Brief description of drawings]

FIG. 1 is a plan view illustrating the configuration of a rotating disk used in an absolute encoder according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a block diagram illustrating a means for controlling a beam tilt angle of an array antenna.

FIG. 4 is a flowchart illustrating a part of a control procedure executed in the controller shown in FIG.

FIG. 5 is a flowchart illustrating another part of the control procedure.

FIG. 6 is a cross-sectional view showing how to read a positioning mark.

FIG. 7 is a sectional view showing another reading mode of the positioning mark.

8 is a sectional view taken along line BB of FIG.

FIG. 9 is a cross-sectional view showing a state in which an arrangement interval of elements for reading positioning marks is changed.

[Explanation of symbols]

M1 to M3, M4 mark 10 rotating disk 20 reading block 21 to 23, 24L, 24C, 24R light projecting elements 21 'to 23', 24L ', 24C', 24R 'light receiving element 30 array antenna 30a to 30f radiating element 31a ~ 31f Phase shifter 34 Drive shaft 35 Drive device 36 Controller

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-9-32958 (JP, A) JP-A 64-1912 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01D 5/00-5/62

Claims (2)

(57) [Claims] 1. An absolute encoder which forms angle recognition marks at a predetermined angular interval on a rotating disk and detects the rotation angle of the disk by reading the angle recognition marks. A mark reading means for reading the positioning marks while forming the positioning marks on the circumference of which the width of the disc in the circumferential direction is set smaller than that of the angle recognition marks at the predetermined angular intervals. 3 are arranged along the circumference, and the size of the arrangement interval of the reading means is an integer multiple of the arrangement interval of the positioning marks plus a length corresponding to a predetermined allowable angle detection error range. An absolute encoder characterized by being set to 2. The length of the allowable angle detection error range is
The absolute encoder according to claim 1, wherein a width of the positioning mark in the circumferential direction is set.